Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D11/00—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space
  • F23D11/36—Details
  • F23D11/40—Mixing tubes; Burner heads
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D11/00—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space
  • F23D11/36—Details
  • F23D11/42—Starting devices
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
  • F23D14/12—Radiant burners
  • F23D14/16—Radiant burners using permeable blocks
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
  • F23C2900/00—Special features of, or arrangements for combustion apparatus using fluid fuels or solid fuels suspended in air; Combustion processes therefor
  • F23C2900/99006—Arrangements for starting combustion
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D2207/00—Ignition devices associated with burner

Definitions

• the basis of the patent is a burner for liquid fuels (hereinafter referred to as oil for example), with which the combustion with oxygen (or an oxygen-containing gas, hereinafter referred to as air) is stabilized on a porous surface, the necessary concept for Mixture preparation and the mode of operation of the burner.
• oil liquid fuels
• air oxygen-containing gas
• the technology of surface combustion is known from the combustion of gases and is already used there for radiant burners, for example for heating industrial halls and for heating buildings (gas wall heaters).
• the advantages of surface combustion are based on the stabilization of the flame in the immediate vicinity of the surface or in the material of the surface structure used.
• the structure of the porous surface offers the possibility of bringing catalytically active substances into contact with combustion gases and thus having a direct influence on the reduction of pollutants in the reaction zone.
• the problem of homogeneous mixture formation in liquid fuels is the heating phase, which is necessary for the evaporation or evaporation of the fuel.
• heating oil concepts for the evaporation or evaporation of liquid films that either run down hot surfaces or are sucked in by capillary forces usually lead to the problem of deposits forming on the surfaces of the evaporator.
• the deposits are reaction products from cracking reactions in the fuel heating oil EL, which occur at temperatures above 400 ° C. Such high temperatures up to the boiling point of the heating oil (380 to 400 ° C) are necessary for a sufficient heat transfer from the evaporator wall to the liquid medium.
• the deposits lead to a deterioration in the heat transfer and thus to the susceptibility of the system to failure.
• the task of mixture preparation is achieved according to the invention by the concept of atomization and evaporation of the fuel in an air stream.
• the task of the required starting ability of the system (when the burner is cold started, the thermal energy necessary for mixture formation (evaporation) is not yet available) is achieved according to the invention by the concept of combining a starting burner (swirl-assisted flame tube stabilization) with a surface burner, and the possibility that To use aggregates of the start burner for the preparation of a fuel-air mixture for the surface burner.
• the required heat input takes place via various mechanisms, which together ensure complete evaporation and prevent the fuel mixture from overheating. This avoids the risk of self-ignition of the mixture in the mixture formation zone.
• the ignition temperature for example of the fuel Heating oil EL (220 ° C) does not ignite the fuel-air mixture under the conditions in this burner concept until the temperatures are much higher (> 500 ° C). This is the only way to achieve homogeneous mixture formation (complete evaporation and over-stoichiometric mixing with atmospheric oxygen).
• the subject of the patent is a burner for liquid fuels, with a central fuel lance, an air supply which can be provided with a swirl device, with an ignition device, with an optional flame tube, with an optional heat exchanger for air preheating and with a porous body for stabilizing a large area or large volume flame.
• the burner works in two operating states. State I, the start mode, is used to preheat the burner to a minimum operating temperature. Preheating can be done by an electric heater. However, with the objective of minimizing the electrical energy consumption - for example in the case of clocked small combustion systems - the construction and mode of operation according to the invention also permit heating by a start-up burner operation.
• the burner works as a flame tube-stabilized burner inside the surrounding surface. This operating state only serves to heat the system to the minimum operating temperature of state II and is designed to be short in time.
• the construction according to the invention allows this burner to be operated with little effort (minimization of the necessary burner units and the electrical energy for supplying the units).
• the flue gases of the start burner in operating state I can be passed directly through the porous body. This improves the heat transfer of the gases to the body to be heated, so that a shortening of the starting phase can be achieved compared to a flow of gases. A mechanical blockage of a second routing of the flue gases of the starting operation is also eliminated.
• the mixture can then be ignited conventionally by ignition electrodes.
• the concept developed also makes it possible to dispense with the external ignition device and to cause the mixture to self-ignite on the surface. This works if the temperature of the surface is sufficiently high in at least one place.
• the area around the end of the flame tube can be heated up sufficiently by the start burner and can easily be made to glow. Due to the relatively large-area ignition area on the (partially or completely glowing) porous body, the start emissions of operating mode II of the combustion on the porous body can be kept low in comparison to punctual ignition sources (e.g. ignition electrodes).
• Appropriate flow control (aim of rapid homogenization of the mixture) and limitation of the temperature (in particular the heat radiation from the glowing surface) can prevent the ignitable oil vapor-air mixture within the burner from igniting.
• auto-ignition can also be achieved by coupling flue gases into the mixture formation zone and / or by dividing the air flow be avoided in a primary and a secondary air flow. Both methods cause the mixture to become inert (reduction of the oxygen partial pressure) and thus an increased ignition delay.
• the flue gases can be fed through openings in the area of the mixture formation.
• the flue gases can be metered by changing the area of the opening, for example using a slide or a plate, even during operation. Temperature control of the change in the area can be carried out efficiently by means of temperature sensors or bimetals, or else in terms of flow technology.
• Flue gases can be drawn in through the impulse of the air in the start burner (short: primary air).
• the primary air can also be preheated by heat exchangers (8) before entering the combustion chamber.
• the oil By introducing the oil into the hot flue gas / primary air mixture, the oil evaporates quickly and mixes homogeneously.
• a partial chemical conversion of the oil can be achieved through the selection of the process parameters (temperature, air volume, flue gas volume).
• the space in the flame tube of the starting burner then acts as a pre-mixing and pre-reaction space.
• additional air in short: secondary air
• the secondary air can also be preheated by heat exchangers (8) before the admixture.
• the pulse of the secondary air can be used to overcome the pressure drop in the matrix of the surface burner.
• the surface burner consists of a porous body (e.g. stainless steel, ceramic). This can be attached to the flue gas outlet opening behind the start burner or cylindrical around it.
• a porous body e.g. stainless steel, ceramic
• the surface burner can be cooled by the secondary air itself.
• the preheating of the secondary air then takes place partially or entirely in the surface burner.
• the surface burner can be coated with surface-enlarging substances and / or with catalytically active substances to influence the chemical conversion of the oil
• the energy required for the evaporation of the fuel and for heating the combustion air can be supplied in various ways. A combination of the ways described can be efficient.
• the combustion air can be heated by a heat exchanger before mixing with the fuel lever.
• the heat exchanger can be arranged in the form of pipes through which the air flows, outside or inside the burner. The arrangement inside the burner prevents the region of the fuel-air mixture from overheating due to heat dissipation
• the heat exchanger is arranged outside the burner, it can also be used to couple low-temperature heat (through flue gas cooling) in high-temperature process processes (chemistry, Stirhng, etc.).
• flue gases are removed from the combustion at a high temperature level, some or all of the heat required to evaporate the fuel can be supplied.
• the flue gases also render the mixture formation zone inert and additionally cool the flame zone.
• the heat is emitted by radiation through the porous body, which is very hot in operating state II, both to the outside (to the medium to be heated, e.g. boiler water) and to the inside.
• This effect can be used to heat the premixing zone if it lies within an area enclosed by the porous body.
• the fuel then evaporates not only through convective heat transfer of the hot air to the oil droplets, but also through direct radiation onto the individual drops.
• the temperature in the premixing zone can be limited by a layered construction of the porous body to protect against self-ignition of the mixture.
• the outer layer of the surface is optimized with regard to the support of the combustion (material, materials, structure).
• the inner layer is optimized with regard to the exact coupling of the necessary heat (heat conduction and radiation properties).

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Spray-Type Burners (AREA)
• Nozzles For Spraying Of Liquid Fuel (AREA)
• Feeding And Controlling Fuel (AREA)

Applications Claiming Priority (5)

Publications (2)

Family

ID=26026864

Family Applications (1)

Country Status (4)

Families Citing this family (5)

Family Cites Families (8)

• 1997
  • 1997-06-24 DE DE59706874T patent/DE59706874D1/de not_active Expired - Fee Related
  • 1997-06-24 WO PCT/EP1997/003311 patent/WO1997049952A1/fr not_active Ceased
  • 1997-06-24 EP EP97929279A patent/EP0906545B1/fr not_active Expired - Lifetime
  • 1997-06-24 AT AT97929279T patent/ATE215678T1/de not_active IP Right Cessation

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events